It is known to provide one or more reference exposures on a filmstrip, in addition to the picture-taking exposures made on the filmstrip, for a variety of uses. For example, the reference exposure might be a gray scale consisting of a series of gray tones extending in regular steps of increasing depth of tone from white (or clear) to black (or opaque). Typically, the gray scale is used during photofinishing as a test object for adjusting exposure and development to give true color balance in making three color separation negatives. The reference exposure typically is made on the filmstrip by the film manufacturer, the photographer, or the photofinisher.
Prior art U.S. Pat. No. 4,260,245, issued Apr. 7, 1981, discloses apparatus for making reference exposures on marginal portions of a filmstrip between successive pairs of metering perforations in the filmstrip. While the metering perforations act as key points to critically locate the reference exposures relative to the picture-taking exposures made on the filmstrip, the marginal portions are relatively small and therefore severely restrict the size of the reference exposures. Preferably, the reference exposures should be the same size as the picture-taking exposures.
A conventional 35mm filmstrip has its metering perforations continue along the entire length of the filmstrip, including the leading and trailing portions of the filmstrip. When a photofinisher wishes to make a reference exposure such as a gray scale on the leading and/or trailing portion of the filmstrip, the photofinisher does not know the exact locations that the picture-taking exposures begin and end on the filmstrip. Consequently, the metering perforations cannot serve as key points to critically locate the reference exposure on the leading and/or trailing portion in conformity with the picture-taking exposures. If the reference exposure is not located in conformity with the picture-taking exposures, control during the printing process is difficult.